Up to now, a capacitive ultrasonic detection device which includes a cell having electrodes disposed at an interval has been known (refer to U.S. Pat. No. 6,430,109). In particular, in recent years, capacitive micro-machined ultrasonic transducers (CMUT) using a micromachining technology have been actively researched. The CMUT transmits or receives an ultrasonic wave by the aid of a lightweight vibrating membrane, and can easily obtain an excellent broadband characteristic even if the transducers are placed in liquid and gas. Attention has been increasingly paid to ultrasonic diagnosis using the CMUT, with higher precision than that in the related-art medical diagnosis modality as a hopeful technology. The ultrasonic receiving function of the CMUT is performed by a capacitive electromechanical transducer and an electric circuit disposed at a later stage. An output of the prestage capacitive electromechanical transducer is caused by a temporal variation of an electrostatic capacitance, and hence the output is a current output. Accordingly, it is general to use a current-voltage conversion and amplification circuit at a later stage.
On the other hand, up to now, a piezoelectric material has been mainly used for the practical ultrasonic transducer. The resolution of the piezoelectric type device is proportional to the frequency, and hence the ultrasonic transducer normally has the center sensitivity in a range of from 3 MHz to 10 MHz. As compared with the piezoelectric type device, the CMUT has a feature of a broad frequency band. However, the piezoelectric type is about to be replaced with the related-art general ultrasonic diagnosis sensor, and hence the center frequency of this sensor is also generally about 3 MHz to 10 MHz. However, in order to effectively use the broad frequency band, a broad band is also required for the later stage electric circuit. The frequency characteristic of the ultrasonic receiving function of the CMUT is generally configured as a band pass type between the cutoff frequency of the capacitance electromechanical transducer and the cutoff frequency of an amplifier circuit. Therefore, the amplifier circuit having the cutoff frequency sufficiently larger than the receive band is frequently used. Regarding this matter, “IEEE Translations on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 55, No. 2, February 2008” discloses an amplifier circuit having a feedback resistance and a feedback capacitance, which is a capacitance parasitically existing in a MOS transistor circuit. As a result, the frequency band of the CMUT disclosed in the above-mentioned publication falls within a range of from 2 MHz to 7 MHz.